1. Technical Field
The present invention relates to a vibration damper, isolator or absorber for use in an automotive air-suspension system having a compressor unit for vehicle height control to suppress the transmission of vibration from a vibration source such as a compressor to a mounting part such as a vehicle body where the compressor unit is secured.
2. Description of Related Art
Among automotive suspension systems are air-suspension systems capable of performing vehicle height control by supplying and exhausting compressed air to and from an air spring by using a compressor. An air-suspension system is provided with a vibration damper so that vibration of the compressor in operation is not transmitted to the vehicle body. A conventional vibration damper provided in an air-suspension system has rubber or a coil spring interposed between a vibration source such as a compressor and a vehicle body, thereby suppressing the transmission of vibration from the compressor or other vibration source to the vehicle body. For example, Japanese Patent Application Publication No. 2004-60524 discloses an example in which the transmission of vibration is suppressed by using rubber.
The above-described conventional vibration damper using rubber or a coil spring suffers, however, from the following problems. If soft rubber is used, vibration damping performance can be improved, but durability degrades. Therefore, rather hard rubber unavoidably needs to be used in actual practice in view of durability. Accordingly, satisfactory vibration damping performance cannot be obtained. When the vibration amplitude of the compressor becomes large at the time of starting or stopping the compressor or when the load changes, the vibration damper using soft rubber may fail to provide a satisfactory vibration damping effect. A vibration damper using a coil spring can provide high vibration damping performance and durability but cannot damp vibration on the compressor side. Therefore, a pipe, hose, electric cable, etc. that are connected to the compressor and so forth are constantly under the influence of vibration and hence likely to be deteriorated. In addition, vibration may have an adverse effect on the compressor and other equipment.
The above-described problems are common to all equipment having an on-board fluid pump such as a pump that supplies a fluid pressure to a brake system mounted on an automobile, a vacuum pump that supplies a negative pressure to a booster used in a brake system, or a hydraulic pump that supplies a fluid pressure to a power steering system.